68000 Motherboard User’s Manual
Rev. A
Page 52 of 54
10
Troubleshooting
Experience dictates…
Symptom
Action
Halt and Reset LEDs remain illuminated
Ensure sufficient input voltage is applied to
allow the Discrete Voltage Supervisor to
release the system from reset. Vcc should
measure as +5VDC and a +4.90V typical
absolute minimum relative to GND.
Verify the Start Vector Selector (SVS) is
configured properly to point to the software
program code.
Verify software is installed properly, with
the correct MSB/LSB order.
Ensure all chips are properly inserted into
their sockets, particularly the 68000.
Verify all jumpers are selected and seated
properly.
Execution halts unexpectedly
"
Red Halt light illuminates
"
Green Run light extinguishes
Check for any loose or bad connections.
These or other problems
Conduct the board level test procedure,
listed in section 12.
11
Design Errata and Commentary
Live and learn. Listed below are various comments and concerns that would have driven
fundamental differences in the design, were it to be done over again.
1.
Both sets of stack connectors could be positioned adjacent to each other in the
layout for improved signal path impedance and signal integrity. Signals present
on other connectors could also be grouped in closer proximity for the same
reason. This system, however, is only designed to operate at 10MHz, and the
opposing stack connector positions offer mechanical advantage.
2.
The location of the clock circuitry could be improved for two advantages. First, it
is currently positioned near the power conditioning circuitry, which acts as a heat
source that causes temperature fluctuation. Second, it is not strategically placed
to minimize clock trace path length between the Stack Interface Connectors and
the system clock signal.
3.
No provision is made in the Clock Synchronization Register to verify that parallel
bits of input data are not transitioning during a latching clock edge. The
implication of this is that if the parallel bits are changing during that clock edge,
some bits captured may reflect newly updated values while others remain with the
Summary of Contents for MB68k-100
Page 1: ...Rev A Grant K c 2011 ...